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  1. audioguru2

    Two PCBs off of one power source

    Please attach the schematic of what "changed out" means. Before you said the volume was too high and you would reduce the value of the 3.3k resistor between pins 4 and 5 to reduce the volume. I don't know what value you tried and I don't know what value you have now.
  2. audioguru2

    Problem With Ultrasonic Motion Detector

    If your LM324 has a low input bias current and the sensors are close enough together then the receiving sensor will pick up amplitude variations of the reflected ultrasonic signal from something that is moving. I think a PIR infrared motion sensor will be much more sensitive and therefore will...
  3. audioguru2

    Two PCBs off of one power source

    The input to the MC34119 amplifier is from where the speaker/headphone jack of the FRS used to be. Nothing has changed how the volume control works. It should adjust the volume smoothly from zero to maximum.
  4. audioguru2

    Adjustable Voltage Reg LM317, Should it be getting this hot ?

    Altronics got the resistor value wrong, the 240 ohms should be 120 ohms with an LM317. 240 ohms is OK for the more expensive LM117. They also got its max output current wrong. Its output current is 1.5A, not just 1A and not 3A.
  5. audioguru2

    Voltage Regulator LM317 to 120ohm or to 240ohm

    Hi Steven, Altronics got it wrong like many people get it wrong. National Semi invented the expensive LM117 and the cheaper LM317. They show 240 ohms with the LM117 and describe what happens if its value is higher than the spec's for the device. The LM317 is supposed to have 120 ohms.
  6. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    No. TI states in their datasheet for the CD4047, "R must be much larger than the Cmos on resistance in series with it". They recommend a minimum value of 10k so that the calculation doesn't need to include the on resistance which varies from device to device. This is ordinary low power Cmos, not...
  7. audioguru2

    Common Collector Emitter Follower

    My circuit has a voltage gain of 500 and has an emitter-follower at its output. The circuit might be a little simpler if it has 3 or 4 transistors.
  8. audioguru2

    Electronic Eavesdropping Devices Detector

    Input offset voltage of an opamp is an error in the balance of its inputs which is amplified by the opamp and causes a DC output voltage when the inputs have the same voltage. Most opamps have a max input offset voltage of 8mV. Single opamps have terminals where a trimpot can be connected to...
  9. audioguru2

    Problem With Ultrasonic Motion Detector

    Hi Nilu, Welcome to our forum. ;D Pin 8 of the LM324 is supposed to be near 0V without a signal. Measure it. The value of R14 is pretty high at 1M. If the bias current of your LM324 is at its max limit of 0.5uA then it will cause the output pin 14 of the LM324 to go high which will turn on the...
  10. audioguru2

    Is this a ceramic cap?

    Yes, it looks like a 0.1uF ceramic capacitor.
  11. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    The resistor and ceramic disc capacitor are correct but the zener diode is in series with the ICs instead of being in parallel with the ceramic disc capacitor.
  12. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    You changed where the zener diode and ceramic capacitor are connected. They should be connected directly across the supply pins if the ICs. Now you have them connected across the high current 12V instead which is wrong.
  13. audioguru2

    battery selector

    You can make a complicated circuit that measures the battery voltage and if it gets low then the circuit replaces the battery with a new one, 4 times. Or you can simply connect 4 batteries in parallel. They will last 4 times as long as one battery, the same as sequencing them.
  14. audioguru2

    Electronic Eavesdropping Devices Detector

    You can cry. You picked a circuit that doesn't work.
  15. audioguru2

    Common Collector Emitter Follower

    Maybe you were told to make a transistor amplifier with a gain of 500 and it must have an emitter-follower at its output. Then make a two or three transistors amplifier. I shouldn't do your homework for you but I have a two transistors amplifier with Q2 as an emitter-follower. It has a 10mV...
  16. audioguru2

    Electronic Eavesdropping Devices Detector

    The project doesn't work. The first opamp amplifies its own input offset voltage.
  17. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    The 0.1uf ceramic disc capacitor is missing from your schematic. The zener diode and the 0.1uF capacitor are across the power supply pins of the ICs.
  18. audioguru2

    Common Collector Emitter Follower

    An emitter-follower doesn't have voltage gain. With a 10mV input, the output is about 9.99mV. A common-emitter single transistor amplifier has a max voltage gain of about 150, but you want a gain of 500. Why not use an opamp?
  19. audioguru2

    White noise generator for mp3 players/ipod

    A radio would pick up a radio transmission of white noise, not an MP3 player.
  20. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    You disconnected the ICs from the positive power. You are supposed to connect a 47 ohm resistor from the positive power to the ICs in series, then connect a zener diode and capacitor across the ICs. An inverter is supposed to be powered by a big car battery, not a lab power supply that doesn't...
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